This invention generally relates to positioning apparatus and methods and more particularly relates to an apparatus and method for remotely positioning an examination or repair probe in a tubular member, which tubular member may be a nuclear steam generator heat transfer tube having a corroded portion to be examined and repaired.
Occasionally, steam generator tubes may corrode or degrade and thus may not remain leak-tight. If through-wall degradation occurs, the radioactive primary fluid flowing in the tubes may leak through the degraded portion and commingle with the nonradioactive secondary fluid surrounding the tubes, a highly undesirable result.
Therefore, the heat transfer tubes are inspected for degradation and then repaired, if necessary, to avoid commingling the radioactive primary fluid with the non-radioactive secondary fluid. Such tubes are inspected by advancing an examination probe (e.g., an eddy current probe or an ultrasonic probe) along the inside diameter of the tube to detect any degradation in the tube wall. If the wall of the tube is degraded, it can be repaired by affixing a repair sleeve to the inside diameter portion of the tube that evinces the degradation. The repair sleeve may be affixed to the inside diameter of the tube by means of an expansion mandrel repair probe, which may be a hydraulic expansion mandrel device. Covering the degraded portion of the tube in this manner prevents commingling the radioactive primary fluid with the nonradioactive secondary fluid. A laser welding repair probe may then be advanced to the location of the sleeve and used to weld the sleeve to the inside diameter of the tube, if desired, in order to securely attach and seal the sleeve to the inside diameter of the tube.
During either examination or repair of the tube, the probe would have been previously connected to an end of a flexible conduit, which is used to axially advance the examination or repair probe to the location of the degradation. The conduit also provides a means through which may pass any required electrical leads connected to the examination probe for supplying power to the examination probe. The conduit may also serve as a means through which any hydraulic fluid is conducted to the repair probe for hydraulically expanding the sleeve into engagement with the tube, when the probe is a hydraulic expander device. In addition, the conduit may serve as a means through which any laser light beams may pass to a laser welding repair probe for laser welding the sleeve to the tube in order to attach and seal the sleeve to the inside diameter of the tube.
The flexible conduit to which the examination or repair probe is attached is wound about a storage drum or take-up reel for compactly storing the conduit when not in use. As the probe axially translates in the tube to perform its examination or repair function, the conduit unwinds from the take-up reel.
However, applicant has observed that as the flexible conduit unwinds from the take-up reel, a portion of the conduit may twist or "kink" Twisting or "kinking" of the conduit is undesirable because such twisting or kinking may be severe enough to sever or break the conduit due to torsional stress induced in the conduit as a result of the twisting or kinking. Breaking of the conduit may in turn cause any electrical leads extending through the conduit to break, thereby making the examination probe inoperable. Moreover, in the instance when the probe is a hydraulically-operated repair probe for purposes of sleeving, breaking of the conduit may interrupt flow of hydraulic fluid to the repair probe, thereby impeding the ability of the repair probe to hydraulically expand the sleeve into engagement with the tube. In addition, in the instance when the repair probe is a laser welding repair probe, breaking of the conduit will interrupt the laser light beam passing through the conduit to the probe, thereby hindering the ability of the repair probe to laser weld the sleeve to the tube. Of course, if the conduit breaks, it must be replaced in order to proceed with the examination or repair of the degraded tube. Replacing the conduit is a time-consuming and costly process. Therefore, there has been a long felt need in the art to prevent or mitigate twisting or "kinking" of the flexible conduit as it unwinds from the take-up reel in order to avoid severing or breaking the conduit.
Moreover, when the previously mentioned laser welding repair probe is used, it must be precisely coaxially aligned within the repair sleeve disposed concentrically within the tube. Precise coaxial alignment of the laser weld head within the sleeve is necessary because misalignment of the laser weld head will otherwise cause uneven or asymmetrical welding of the sleeve to the tube as the laser weld head rotates within the inside diameter of the sleeve. Such asymmetrical welding may compromise the ability of the weldment to securely affix and seal the sleeve to the inside diameter of the tube. Therefore, another problem in the art is to provide precise coaxial alignment of the laser welding repair probe with the sleeve in order to precisely weld the sleeve to the tube.
A device for checking bent tubes by means of a pneumatically propelled eddy-current probe is disclosed in U.S. Pat. No. 4,633,177 titled "Device For Checking Bent Tubes By a Probe, Such As A Pneumatically Propelled Eddy-Current Probe" issued Dec. 30, 1986 in the name of Bernard David, et al. This patent discloses a probe including a cable having floaters for guiding the cable in the tube, the cable being wound about a coiler. However, this patent does not appear to disclose a solution to the problem of preventing or mitigating twisting or "kinking" of the cable as it unwinds from the coiler. Moreover, this patent does not appear to disclose a solution to the problem of precise coaxial alignment of a repair probe within a sleeve concentrically disposed in a tube.
An apparatus and process for positioning and oscillating heater probes within heat exchanger tubes of a nuclear steam generator is disclosed in U.S. Pat. No. 5,061,176 titled "Apparatus And Process For Simultaneously Positioning And Oscillating A Plurality Of Probes In The Heat Exchanger Tubes Of A Nuclear Steam Generator" issued Oct. 29, 1991 in the name of Paolo R. Zafred, et al. and assigned to the assignee of the present invention. This patent discloses a plurality of probe drivers, wherein each driver includes a pneumatically operated, bladder-type gripper for selectively gripping and ungripping the push-cable of one of the heater probes. However, this patent does not appear to disclose a solution to the problem of preventing twisting or "kinking" of a flexible conduit as it unwinds from a take-up reel. Moreover, this patent does not appear to disclose a solution to the problem of precise coaxial alignment of a repair probe within a sleeve concentrically disposed in a tube.
Therefore, what is needed are an apparatus and method for suitably positioning an examination or repair probe in a tubular member, which tubular member may be a nuclear steam generator heat transfer tube having a corroded portion to be examined and repaired.